This application relates to image processing to provide electronic enlargement and display thereof by video technique. More particularly, it relates to image processing logic circuitry ("logic") and to an image processing station and methodology utilizing such so-called logic to provide enlargement ("zooming") of a digitally stored image in real time video display, with the image being zoomed instantaneously from the viewer's perception, i.e., "on-the-fly," and otherwise selectively controlled, as in image screen position ("pan") and contrast, while being viewed.
In high resolution image display systems, e.g., 1024.times.1024 image elements (pixels), the image is represented by a total of 2E20 pixels. It has heretofore been proposed to provide digital processing, whether by dedicated circuitry or microprocessor, for carrying out calculations for the determination of pixel intensity levels at positions in an enlarged image matrix. Such processing involves both position and intensity calculations. The typical time required for such calculations in known previous processing systems has been on the order of seconds, which precludes real time, on-the-fly display of the processed image. That is, the time required for providing the processed data exceeds one video frame period, as typically 1/60 sec. (noninterlaced display). The visual effect in zooming an input image for video display is, therefore, discontinuous. It is greatly desired that image zooming be carried out in real time display, i.e., completely generated from one video frame to the next, so that all zoom processing necessary for achieving a zoomed image display can be carried out within a single video frame period.
It has until the present invention been considered impossible to achieve video processing of high resolution video images from frame to frame because of the large number of calculations required per frame period. For example, Tabata et al U.S. Pat. No. 4,610,026 refers to processing times in the order of seconds for 10E6 image elements. Typically, the calculations are required to be stored as converted image data in a secondary memory, as the processing time precludes direct display.
There are various processing methods for carrying out such calculations, among which is the method of bilinear pixel interpolation, herein referred to for convenience as "BPI", with which the present invention is concerned. Shiratsuchi U.S. Pat. Nos. 4,774,581 and 4,792,856 are illustrative. In such method, the intensity at a pixel in the interpolated image is calculated based only on four pixels in the uninterpolated image whose centers surround (to the upper left, lower left, upper right and lower right, respectively) the point at which intensity is being interpolated. The interpolation is linear in both the horizontal and vertical direction. Typically, for each interpolated data point a total number of six additions and three multiplications are needed. Thus, for each of 10E6 data points, carried out in one frame period (1/60 sec. corresponding to noninterlaced display), a total number of 5.4.times.10E8 arithmetic operations per sec. is necessitated for the intensity calculations alone. Additional calculations are required for the position determinations. The possible processing rate for such calculations is well illustrated by Anderson et al U.S. Pat. No. 4,661,987 for merely a 500.times.500 interlaced (1/30 sec. frame) display, viz. 6.25.times.10E10 operations. Said Shiratsuchi U.S. Pat. Nos. 4,774,581 and 4,792,856 use serial processing of data by BPI for similar 1/30 sec. interlaced (1/30 sec. frame rate) display with comparable television (512.times.512) resolution.
Until the present invention, it is believed that the BPI method has not been used for achieving real time, on-the-fly image zooming of a high resolution (1024.times.1024 pixels) display. Zoomed pixel data must be provided at processing rates high enough for real time display (i.e., at least at the display frame rate).
Among the several objects of the invention are the provision of image processing circuitry and an image station providing video display of a high resolution (e.g. 1024.times.1024) input image using zoom processing for providing real time, on-the-fly image zoom processing of the input image without using secondary memory for intervening storage of the results of the zoom processing, but instead providing the processed data for direct screen display "on-the-fly" wherein the time required for providing processed data does not exceed one video frame period, and whereby each frame of the processed image may have a different zoom factor; which zoom processing circuitry and station uses bilinear pixel interpolation; which can be utilized to marked advantage for receiving, displaying, and analyzing images for medical and other applications requiring high resolution display, such as radiographic images; which permits contrast manipulations of such images as well as pan (position shifting) manipulation of the zoomed image; which does not require the use of auxiliary, e.g. secondary, memories for storage of the processed images but instead provides direct and instantaneous display of them in a real time mode, while permitting the user to control the image precisely and continuously as to zoom factor, contrast manipulations (such as "window and level"), and pan (i.e., display of selected regions of the zoomed image).
A related object of the invention is the provision of such zoom processing circuitry permitting the start position of each zoom-processed pixel to be calculated during the frame period to such a degree of precision that the processed image may be panned smoothly during its real time video display and continuously without user-apparent jumping or discontinuity from one frame to the next, yet permitting the zoom factor to be changed from any one frame to the next.
Briefly, the invention provides image processing apparatus, and an image display station utilizing such apparatus, for selective real time zooming of a digitized high-resolution input image, comprising image memory means for storage of input data representing the input image for making available for pixel processing in each of subsequent clock intervals successive groups of adjacent pixel data values of the input data, throughout a portion to be displayed of the input image, the apparatus further comprising at least user zoom control means for selectively establishing a zoom factor for zooming of the input image. Pixel processing means provides bilinear pixel interpolation processing of said successive groups of adjacent pixel data values throughout the displaced portion of input data within the time period of a single video display frame in accordance with a zoom factor established for such video display frame. Output means provides the pipelined processed groups of data for on-the-fly real time video display, whereby each of successive video frames may have a different such zoom factor.
The invention is disclosed in Disclosure Document 215004, filed Nov. 28, 1988, continued preservation of which is requested.